Pipettes tips are small tubes made of plastic which are used in the laboratory for metering liquid samples, preferably within the range of 0.1 μL to 100 mlL. They have a bottom opening for liquid and a top opening for air, and the cross-section of the pipette tips generally increases from the bottom aperture opening toward the top aperture opening.
To meter liquid, the top end of the pipette tip is connected to a pipette such that the top opening is joined to a pipette displacement apparatus for air. The opening of the pipette tip is clamped onto a shoulder of the pipette, or clamped in a hole of the pipette. A channel terminates in the face of the shoulder or respectively in the base of the hole, and the channel is connected to the pipette displacement apparatus. The displacement apparatus of a piston stroke pipette is a cylinder with a piston which can move therein. With the assistance of the displacement apparatus, an air volume is shifted such that a specific amount of liquid is drawn into the pipette tip and discharged therefrom. Fixed volume pipettes with a constant metering volume have a constant displacement, and variable pipettes with an adjustable metering volume have an adjustable displacement. With direct displacement pipettes, a piston is integrated in the pipette tip which is driven by the displacement apparatus.
After being used, the pipette tip is removed from its seat on the pipette, for which purpose the pipette can have an ejector that, upon being actuated, pushes the pipette tip off of its seat. Then the pipette can accommodate a new pipette tip. This prevents sample liquid from one metering from carrying over into a subsequent metering.
In order to affix pipette tips on the seat of a pipette, pipette tips are provided on devices for providing pipette tips. These devices have a perforated plate that is also termed a “tray” or “wafer”.
Furthermore, these devices comprise a bottom part which is designed as a box that is closed at the bottom and open at the top, or a rectangular frame (also termed a “rack”) that is open at the bottom and the top. A perforated plate equipped with pipette tips can be mounted from above on a mounting edge of an insertion opening in the bottom part so that the pipette tips extend into a holder in the bottom part.
The pipette tips can be removed from a device for providing pipette tips by pressing the seat of a single channel pipette, or the seats of a multi-channel pipette, onto or into the top ends of the pipette tips, individually or several at the same time.
Devices for providing pipette tips are known in which the bottom part can be reused after all of the pipette tips have been removed. For this, the perforated plate is removed, possibly together with the used pipette tips that have been reinserted therein, and discarded. With the assistance of refill packs, the holder is equipped with fresh pipette tips. The refill packs can comprise several perforated plates that are equipped with pipette tips. Refill packs are known, for example, with one or more perforated plates filled with pipette tips arranged in folding boxes or cardboard frames, or in simple plastic boxes or plastic frames.
With the refill packs according to WO 92/01514 A1, U.S. Pat. No. 5,366,088 and WO 00/518899 A1, a perforated plate equipped with pipette tips is releasably attached to the top edge of a shell made of plastic, wherein the pipette tips extend into the shell. An additional perforated plate is arranged thereabove with pipette tips that extend into the pipette tips in the bottom perforated plate and that are releasably attached at the edge to the bottom perforated plate. Additional plates with pipette tips are correspondingly arranged thereabove, and the arrangement is covered at the top by a lid made of plastic which is releasably attached to the topmost perforated plate.
In designs of these refill packs, the lid can be used to transfer the perforated plates equipped with pipette tips from the refill stack into the holder, and can then be placed on the topmost perforated plate of the refill stack in order to protect the opened refill pack.
The disadvantage of these refill packs is that the pipette tips are at least partially unprotected and can become contaminated when moving the perforated plates to a holder.
Furthermore, sterile pipette tips are offered. In applications in which sterility is important, they must not be contaminated before use (or they must be autoclaved before use). Filter pipette tips are generally offered sterile because the filter materials do not withstand the temperatures during autoclaving.
Sterile pipette tips are handled in robust disposable boxes to be worked through, and not in refill packs for moving into a box or frame. In contrast to reusable boxes, disposable boxes are disposed of after all of the pipette tips have been removed. They have a complex design and are therefore expensive to produce, and a large amount of packaging waste is generated by the user.
EP 2 535 109 A2 describes a device for providing pipette tips which comprises a refill pack and a holder. The refill pack has a perforated plate with a plurality of holes, pipette tips inserted into the holes, a shell that covers the pipette tips at the bottom with a rigidity up to 300 N/mm, and a cover that covers the pipette tips at the top. The holder has a seat for inserting the refill pack. The refill pack and holder have means for bracing that brace the refill pack inserted into the seat. By means of the shell and the cover, the pipette tips inserted into the perforated plate are covered at the top and bottom and protected from contamination when refilling the holder. The rigidity of the shell is so low that it is easily producible using little material. The forces when pipette tips are received by a pipette are deflected into the holder by the bracing means. One design has means for latching the cover and shell. Furthermore, the holder has a bottom part with the seat and a lid that covers the refill pack inserted therein and has an articulated connection with the bottom part. The lid of the holder and the cover of the refill pack have means for latching that can be latched to each other by closing the lid when the refill pack is inserted into the seat.
When the lid is opened, the cover is also opened since the force for releasing the latching between the lid and cover exceeds the force for releasing the latching between the cover and shell. The protection of the refill pack from contaminants is improved, and the pipette tips are protected from contact with the lid of the holder. The disadvantage is that the user must put his hand inside the lid before inserting a new refill pack in order to release the latching with the cover. A comparatively high force must be exerted for this. This makes handling difficult and can cause the holder to become contaminated.